you can get ball and socket armatures from animation suppiles they have a small range of armatures i highly recomend this website it also sells software, rigging tiedowns and more oh they have a do armature as well

Firstly, attach a small magnet to the bottom of each leg on the armature and then place it on a magnetic surface. This will add weight to stabilise your character and means that it will stand freely far easier.

You can also use tie downs, which entails putting a bolt in the foot of your character and having holes across the entirety of your set. This way is obviously very impractical and usually ruins a very nice set.

Finally, you can make a character walk without even making them leave the ground! Sounds ridiculous I know, however, it works, and does so very well!

Here is an image Cavor posted some time ago (It was pretty arduous task going through my animation/sculpture folder to find this image hehe) showing how to get an effective walk cycle without your character leaving the ground.

I hope this gives you a clearer view on how to get a decent looking walk cycle when animating. If you have anymore questions I'll be here to answer them as well!